Studies on the Physiology and Pathogenicity of Sclerotium Rolfcii Sacc. Causing Fruit - Rot of Tomato (Lycopersicum Esculentum Mill.)
Date
1965-06
Authors
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Journal ISSN
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Publisher
University of Ghana
Abstract
Salerotium rolfsii Sacc. grew best at 27 to 32 C,
and maximum infection of tomato fruits occurred at
32°C„ S^_ rolfsii showed a double maximum of growth in
relation to pH: a major peak at pH 1+.8 and a minor one
at pH 9.31 with a minimum of pH 8.2 in between. Light
had no effect on growth. Growth occurred only at 100$
R. H. whereas infection of tomato fruit occurred at a
relative humidity of 957° and above. A moisture level
of 55% W. H. C. of soil caused the greatest infection,
and degree of infection diminished with a deviation in
% W. H. C. in either direction from this level. Even though externally supplied thipmine v/as not
essential for initiation of growth, subsequent development
depended on it„ Thiamine at 25 Mg and 50 Aig supported
the greatest growth. rolfsii was capable of
using simple as well as complex carbohydrates as
sources of carbon. Starch supported the best growth,
followed by Maltose, Fructose and Glucose, whilst galactose
and cellulose gave the poorest vegetative growth.
Of the nitrogen sourcjig^Peptone and Asparagine
were best used by the' fungus,"’and the least suitable
was Alanine. S. rolfsii can enter the host through the intact
fruit skirf. Rate of infection increased almost directly
proportional to increase in size of inoculum.
Prior to infection, rolfsii formed infection cushions
on the fruit wall. Penetration was achieved by
hyphae, emerging from the infection cushions, mechanically
piercing through the cuticle and epidermis.
Growth within the fniiit was both intercellular and
intracellular. Pericarp cells were ultimately dissolved
by substances produced by the fungus leaving the
dead epidermis and cuticle intact. The disease was not
seed borne.
Tomato fruits of all ages were infected, and
Molokai was the only Ghanaian tomato variety whose
fruits were completely resistant to 3. rolfsii.
Description
Thesis(MSc)-UNiversity of Ghana, 1965